1. Field of the Invention
This invention relates to a self-conscious type examining apparatus.
2. Description of the Prior Art
The conventional self-conscious type eye examining apparatus used for sight measurement in ophthalmology, as shown in FIG. 1 of the accompanying drawings, is formed substantially symmetrically and set so that the centers of the view field windows 1 of left and right lens chambers R are coincident with the examinee's eyes, and the operator changes lenses within the view field windows 1 and chooses appropriate lenses while asking the examinee looking into a sight chart lying on this side of FIG. 1 through the view field windows 1 as to how the examinee sees the chart. The change of the lenses is accomplished by means of handles 2 to 6. Holding plates for lenses are contained in the lens chambers R and each of the holding plates 14 to 17 is in the form of a disc centered about a shaft 18. The disc 14 holds on the same circumference an opening for releasing the view field, a shield plate for shielding the view field, and optical elements including both-eye examining lenses such as a polarizing lens, a prism lens, etc. and a prism diopter measuring lens such as a Maddox rod. The disc 14 is rotated by the handle 2 and desired optical elements are inserted into the view field windows 1. Chosen optical elements are displayed by display plates 8. Lenses having different refracting characteristics are held by the discs 15 to 17 at equally divided angles about an axis correspondingly to the number of lenses. Eleven different spherical lenses 15' are held on the disc 15 with a spacing of 3D therebetween from -18D to +15D (D indicates diopter). Rotation of the disc 15 may be accomplished by means of the handle 6 through a gear, not shown. Eleven different spherical lenses 16' are held on the disc 16 with a spacing of 0.25D therebetween from -1.00D to +1.75D. Rotation of the disc 16 may be accomplished by means of the handle 5 through a gear, not shown. The spherical powers of the lens chambers R overlap in the view field windows 1 and become the value of the sum of the diopters of the two lenses 15' and 16' and as a result, making lenses of different characteristics appear in the view field windows 1 with a spacing of 0.25D from -19.00D to +16.75D becomes possible. To change the power continuously, it is necessary to rotate the discs 15 and 16 at the same time and therefore, an intermittent mechanism (not shown) such as a Geneva mechanism is generally used between the discs 15 and 16. The powers of the spherical lenses are displayed by display windows 7. Nine different astigmatic lenses are held on the disc 17 with a spacing of 0.25D from 0D to -2.25D, and each of them is contained in a gear 19 rotatable in the disc 17 so that the cylindrical axis thereof is rotatable. The disc 17 fixed to a gear 21 is made rotatable by rotating the gear 21 by means of the handle 4 through a gear, not shown. Cylindrical powers are displayed by display windows 9. As regards rotation of the cylindrical axis, a gear 20 is made rotatable by means of the handle 3 through a gear, not shown, and the gear 20 is coupled to all gears 19 containing cylindrical lenses therein and as a result, rotation of all cylindrical lenses about the axes thereof are made possible by rotation of the handle 3. Cylindrical axes are displayed by display plates 10. In the apparatus of this type, devices 11 called cross cylinders for precisely measuring the cylindrical power and cylindrical axis are provided outside the lens chambers R. The cross cylinders 11 are usually provided outside the view field windows 1 (at the positions shown) and are rotated about the shafts 13 only when required, whereby they are inserted into the view field windows 1 to effect measurement. The cross cylinders 11, as shown in FIGS. 3 and 4 of the accompanying drawings, are cylindrical lenses in which the absolute values of the maximum power and the minimum power are equal to each other and differ in sign and the principal meridan direction indicative of the maximum power is orthogonal to the principal meridian direction indicative of the minimum power, and usually, 0.25D or 0.5D is used as the absolute value (the Figure shows a cross cylinder of 0.25D). As shown in FIG. 3A, the principal meridian (the direction of +0.25D) indicative of the maximum power is adjusted to the cylindircal axis direction B of the examinee, the cross cylinder 11 is reversed by means of a knob 12 (FIG. 3B) and precise measurement of the cylindrical power is effected before and after the reversal by comparing the manners in which the chart is seen by the examinee. Precise measurement of the cylindrical axis is accomplished by adjusting the principal meridian indicative of the maximum power (the direction of +0.25D) to the direction of 45.degree. with respect to the cylindrical axis direction B of the examinee as shown in FIG. 4A (rotating the cross cylinder 11 by 45.degree. relative to FIG. 3B), and then reversing the cross cylinder (FIG. 4B), and comparing the manners in which the chart is seen before and after the reversal. During measurement, when the disc 17 is rotated to interchange the cylindrical lens or the gear 19 is rotated to change the cylindrical axis, it is necessary to again effect the examination by the cross cylinders. For the purpose of facilitating this reexamination, the cross cylinders 11 and the cylindrical axis of the cylindrical lens on the disc 17 are always operatively associated with each other and, when the cylindrical axis is rotated by means of the handle 3, the cross cylinders 11 are likewise rotated.
In this manner, in the conventional cross cylinders 11, the position of the reversing knob 12 during measurement of cylindrical power (FIG. 3) and the position of the reversing knob 12 during measurement of cylindrical axis (FIG. 4) differ from each other by 45.degree. and, when the cross cylinders 11 are rotated to rotate the cylindrical axis, the knob 12 also is rotated together therewith and therefore the position of the knob is not fixed, and this has led to poor operability. Also, the knob 12 must be operated so as not to obstruct the view field of the examinee and this has led to the disadvantage that the examiner is compelled to assume an unnatural posture.